if you just wanna show an information to the user use an sap.m.MessageBox.
sap.m.MessageBox.information(
"Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat"
);
If you need sap.m.Popover go for sth. like this:
contentWidth="{= ${device>/system/phone} ? '100%' : '20%'}"
<core:FragmentDefinition xmlns="sap.m" xmlns:core="sap.ui.core">
<Popover title="Popover" placement="Bottom" contentWidth="{= ${device>/system/phone} ? '100%' : '20%'}" class="sapUiContentPadding">
<Text
text="Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet."/>
</Popover>
</core:FragmentDefinition>